This invention relates to the production of woven sewn fiber reinforcements for structural components, and is particularly concerned with procedure for continuously producing an assembly of layers of plies of woven cloth having different fiber orientation patterns, and securing the plies together in a predetermined position with respect to each other.
Most structural type composite parts are made from multiple plies or layers of "B" stage resin impregnated woven cloth or unidirectional type fiber (graphite, boron, Kevlar, fiberglass or mixtures of such materials). The plies are laid in place one layer at a time until the total number of plies have been positioned to a prescribed fiber ply orientation pattern. This layered assembly is then cured under heat and pressure by conventional processes dependent on the resin system in use. These fiber reinforced resin or plastic components have numerous applications, particularly as structural components in airplanes, ships and automobiles.
However, the individual ply-by-ply layup time for assembling a required fiber pattern is time-consuming and expensive, and further is subject to human error in fiber ply count and fiber ply orientation.
Many prior art patents disclose the production of various forms of woven and unwoven materials or cloths which are impregnated with resin. Many of the resin impregnated structures so produced, however, are not designed for use as high strength structural components, but are employed in other applications, for example as acoustic materials.
Thus, for example, U.S. Pat. No. 3,481,427 describes a three dimensional woven fiberglass fabric which, when impregnated with resin and cured, gives a rigid porous panel structure for acoustic requirements. A sandwich with porous skin on one side and solid skin on the other side, and connecting fluted webs, can be woven at once. The weaving is in the form of an over/under pattern that is not optimized for strength but for sound absorption.
U.S. Pat. No. 3,700,067 describes a three dimensional woven porous sheet formed from an integrally woven fiber which, when impregnated with a low flow resin and cured, gives a rigid yet porous panel. Its intended use is sound absorption.
It is an object of the present invention to provide a woven sewn fiber reinforcement as an integral assembly, which can be impregnated with resin and employed as a structural component. Another object of the invention is to provide procedure for laying up a plurality of layers or plies of woven cloth having different orientation patterns, and securing the plies together in a predetermined position with respect to each other. Yet another object is the provision of procedure for continuously arranging a plurality of layers or plies of woven fiber reinforcement cloth, and continuously securing together the respective layers or plies to form a unitary woven reinforcement having high modulus and high strength. A still further object of the invention is to carry out the above noted procedure for producing an integral woven reinforcement by inexpensive and simple operations.